Although some scientists define animal migration as any animal movement, this definition becomes cumbersome because it does not distinguish between small-scale daily movements, annual migrations, and irrupting dispersions. Mobile animals tend to move frequently, and migration should be distinct from emigration (directional one-way movement) and dispersal (non-directional one-way movement), and it should refer primarily to regular round trip movement that happens at least once in the life span of the organism. Migration is a spatial behavior pattern that allows animals to locate themselves in the most favorable portions of their habitat for as long as necessary. Such favorable conditions may vary according to season or life history, but in both cases it is related to adaptive fitness. This allows the organism to take in nutrients in excess of energy expenditures and to successfully reproduce.

Generally animal migration can be divided into two areas of study: the behavioral aspects...